The invention is based on a measuring instrument for determining an angle of rotation of a device as defined hereinafter. In a known measuring instrument of this type (German Offenlegungsschrift 39 16 864), U.S. Pat. No. 5,027,067, the coil body is slit on its end, which creates two semicircular cores. One sensor coil is wound onto each of these cores which are surrounded by a sleeve body. The sleeve body either has a slit or has a zone of electrically nonconducting material. Since the measuring instrument operates by the so-called eddy current principle, tumbling motions that change the spacing between the coil and the inside of the sleeve body can adulterate the measurement signal. This worsens both the accuracy of the measurement signal and the detection of the angle of rotation.